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1   /*
2    * Copyright 2014 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   https://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  
17  package io.netty.handler.codec.socksx.v5;
18  
19  import io.netty.buffer.ByteBuf;
20  import io.netty.channel.ChannelHandlerContext;
21  import io.netty.handler.codec.DecoderException;
22  import io.netty.handler.codec.DecoderResult;
23  import io.netty.handler.codec.ReplayingDecoder;
24  import io.netty.handler.codec.socksx.SocksVersion;
25  import io.netty.handler.codec.socksx.v5.Socks5CommandRequestDecoder.State;
26  import io.netty.util.internal.ObjectUtil;
27  import io.netty.util.internal.UnstableApi;
28  
29  import java.util.List;
30  
31  /**
32   * Decodes a single {@link Socks5CommandRequest} from the inbound {@link ByteBuf}s.
33   * On successful decode, this decoder will forward the received data to the next handler, so that
34   * other handler can remove or replace this decoder later.  On failed decode, this decoder will
35   * discard the received data, so that other handler closes the connection later.
36   */
37  public class Socks5CommandRequestDecoder extends ReplayingDecoder<State> {
38  
39      @UnstableApi
40      public enum State {
41          INIT,
42          SUCCESS,
43          FAILURE
44      }
45  
46      private final Socks5AddressDecoder addressDecoder;
47  
48      public Socks5CommandRequestDecoder() {
49          this(Socks5AddressDecoder.DEFAULT);
50      }
51  
52      public Socks5CommandRequestDecoder(Socks5AddressDecoder addressDecoder) {
53          super(State.INIT);
54          this.addressDecoder = ObjectUtil.checkNotNull(addressDecoder, "addressDecoder");
55      }
56  
57      @Override
58      protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
59          try {
60              switch (state()) {
61              case INIT: {
62                  final byte version = in.readByte();
63                  if (version != SocksVersion.SOCKS5.byteValue()) {
64                      throw new DecoderException(
65                              "unsupported version: " + version + " (expected: " + SocksVersion.SOCKS5.byteValue() + ')');
66                  }
67  
68                  final Socks5CommandType type = Socks5CommandType.valueOf(in.readByte());
69                  in.skipBytes(1); // RSV
70                  final Socks5AddressType dstAddrType = Socks5AddressType.valueOf(in.readByte());
71                  final String dstAddr = addressDecoder.decodeAddress(dstAddrType, in);
72                  final int dstPort = in.readUnsignedShort();
73  
74                  out.add(new DefaultSocks5CommandRequest(type, dstAddrType, dstAddr, dstPort));
75                  checkpoint(State.SUCCESS);
76              }
77              case SUCCESS: {
78                  int readableBytes = actualReadableBytes();
79                  if (readableBytes > 0) {
80                      out.add(in.readRetainedSlice(readableBytes));
81                  }
82                  break;
83              }
84              case FAILURE: {
85                  in.skipBytes(actualReadableBytes());
86                  break;
87              }
88              }
89          } catch (Exception e) {
90              fail(out, e);
91          }
92      }
93  
94      private void fail(List<Object> out, Exception cause) {
95          if (!(cause instanceof DecoderException)) {
96              cause = new DecoderException(cause);
97          }
98  
99          checkpoint(State.FAILURE);
100 
101         Socks5Message m = new DefaultSocks5CommandRequest(
102                 Socks5CommandType.CONNECT, Socks5AddressType.IPv4, "0.0.0.0", 1);
103         m.setDecoderResult(DecoderResult.failure(cause));
104         out.add(m);
105     }
106 }